Nordic Structures manages large forests of black spruce located within the boreal ecosystem of Northern Quebec’s Chibougamau region. These slow-growing trees have a high fiber density but a small mean diameter of 107 mm (4.2 inches), limiting their use in construction. However, Nordic Structures has used these characteristics to develop high density, homogenous Glulam products with sawn lams of 22 mm x 44 mm.
To expand this operation and keep up with the growing forest industry, logistical challenges needed to be addressed. The Maicasagi River was one of these, requiring a bridge with a span of 67.4 m that could handle logging trucks with traffic loads of 1800 kN (180 t custom truck, CF3E-140t). Under a tight project schedule, engineers solved the issue by using a two box-girder beam design, each composed of block-bonded (4-piece) Glulam flanges and cross-laminated timber (CLT) webs. Using self-tapping screws, the outer webs were directly connected to the flanges and the inner webs were attached with a steel member using ring nails beside the self-tapping screws. Facing tension forces at the lower flange and compression forces at the upper flange at the assembly detail of the prefabricated elements, self-tapping wood-steel screws were used on site for the bottom part and bolts for the top part.
While a timber bridge is very thematically appropriate in this situation, it was merely cost and schedule that determined the engineers’ choice of material, as steel would have been more expensive, and concrete would not have met the time constraints due to limited prefabrication. The Maicasagi Bridge thus demonstrates the great competitiveness of modern mass timber design, and was awarded with the Prix d’Excellence Cecobois in 2013.
Read more about it in this SNC-Lavalin article (Fr)!
Register for a Technical Learning Session
Sign up for MTC Newsletter and keep up to date with all our progress.